2020 Volume 20 Issue 1 Pages 55-60
Spectral hemispherical transmittance of piling quartz glass plates for hemispherical irradiation was estimated by integrating directional transmitted radiant energy measured through a grated spectrometer. The transmittance was consistent with the numerical result based on ray-tracing model except periodic fluctuation (ripple) found especially in the wavelength less than 2.0μm. The ripple resulted from comprehensive polarization characteristics of the spectrometer with sapphire window and was generated for polarized radiation fundamentally. Since the spectral shape between s and p components were upside-down mutually, they could be canceled in the case of random irradiation. As the number of the plates or transmitted angle was large, irradiation into the spectrometer was more polarized and therefore the ripple in the spectral output appeared more remarkably. However, under the conditions of 8 plates the transmittance could be regarded to be reasonable. In addition, mechanism for generation of the ripple was clarified theoretically using Stokes parameter and Mueller matrices. As a result, it was cleared that the ripple didn’t appear at all if parallel ray was transmits through the sapphire vertically.
